An electric storage device is in some cases equipped with a current interruption device that interrupts a current path connecting an electrode assembly in a casing and an external terminal provided in the casing when the electric storage device is overcharged or when a short circuit occurs in the electric storage device (see for example, Japanese Patent Application Publication No. H08-185849 (1996), and Japanese Patent Application Publication No. H08-115715 (1996)). The current interruption device includes an internal terminal plate and a conductive plate facing the internal terminal plate. An outer circumferential part of the conductive plate is connected to an external terminal plate, while a center part of the conductive plate is connected to a center part of the internal terminal plate. An outer circumferential part of the internal terminal plate is connected to the electrode assembly. When pressure within the casing rises, the conductive plate separates from the internal terminal plate to interrupt electric conduction between the conductive plate and the internal terminal plate, thereby interrupting a current flowing between the electrode assembly and the external terminal.